Five
years after she married Gerald D., a wealthy oil executive, Carole
D., a former international model, met Michael H., and in an extramarital
affair, conceived a child with him. Michael H. et al.
v. Gerald D., 491 U.S. 110 (1989). After the child,
Victoria D., was born, Carole confirmed by genetic testing that
the little girl was Michael’s. Separating from her
husband, she, Victoria, and Michael, moved to St. Thomas, Virgin
Islands, where they lived together as a family unit. Several
months later, Carole left Michael for a third man, Scott K. For
the next several years, Carole and Victoria maintained contact
with all three men, living with each at different times of the
year. Finally, Carole reconciled with Gerald, who acknowledged
Victoria as his child, despite genetic evidence to the contrary. Michael
H. filed suit, seeking visitation rights with his biological
daughter against the wishes of Gerald. He argued that fatherhood
was a fundamental and protected constitutional right. The
state court awarded Michael limited privileges to see Victoria,
but Gerald appealed.

On appeal to the U.S. Supreme Court, Michael was denied any
contact with Victoria whatsoever on the grounds of the so-called
paternity presumption rule, a century old law, enacted originally
in 1872, providing that “[t]he issue of a wife cohabiting
with her husband, who is not impotent, is indisputably presumed
to be legitimate.” By California law, unless
the parents disputed a child’s paternity within a two year
period of time, the child’s paternity was irrefutably determined
to be the husband’s. Victoria was deprived of her
biological dad, and Michael, of fatherhood.

The paternity presumption rule has an equally unkind side for
the duped husband. After two years had passed, had Gerald
refused to support Victoria as his daughter, Carole could have
gotten a court order establishing him as the father, compelling
him to pay child support. Its nineteenth century predecessor
was unforgiving, and there was no grace period during which poor
Gerald could contest the paternity presumption – even when
it was known to be an absolutely incorrect determination.

What is the reason for a rule that divests a biological father
of his child, and then assigns the role and duty to support it
to a completely unrelated man? To come up with answers to this
question, and others like it that relate to family and matters
of sexuality, we are going to use the tools of evolutionary theory
and how they apply to human behavior.

The explanation for rules in general is straightforward. Society
would not be possible without a code of conduct that all its
members agree to follow. As Thomas Huxley in Evolution
and Ethics observed, “wolves could not hunt in packs
except for the real, though unexpressed, understanding that they
should not attack one another during the chase.” Rules
facilitate cooperation and let people know how they are expected
to behave. Under the paternity rule at issue in Michael
H, the husband expects that any child his wife bears will
be presumed to be his own, and that he will have the duty to
support it, irrespective of who is its biological father. This
may make him more vigilant and attentive to the needs of his
wife.

Paternity presumption is premised on institutionalized monogamy. When
males and females pin their reproductive success on a monogamous
relationship, it becomes important to know that the offspring
belong to them, and that this fact is insured by the law. In
primates, several different explanations have been given for
the existence of monogamy, rather than promiscuity or polygamy. One
theory proposes that monogamy is favored when economic conditions
prohibit a male from monopolizing more than one female. A
second theory states that, because of protracted infancy, two
parent childcare is more effective than maternal care, alone. A
third explanation is that males in a monogamous relationship
will protect their offspring from infanticide by unrelated males. Thus,
the adoption of monogamy has a clear advantage for reproductive
success.

In humans, it has been argued that monogamy is the cultural
epitome, evolving from other forms of reproductive relationships. Led
by Lewis H. Morgan – who had published a pioneering study
of the matrilineal system of the Iroquois Indians in the Eastern
United States – nineteenth century anthropologists believed
that society had passed through certain states, beginning with
a state of promiscuity, where men and women freely engaged in
sex, and lived together in clans of related individuals. This
stage, the theory went, was succeeded by matriarchy. In
it, women were believed to have held the power in society, and
kinship was determined exclusively by maternal descent. For
economic and other reasons, it was believed that matriarchy was
replaced by the monogamous nuclear family, with a paternal head,
and the female dominated by the male.

Frederick Engels, cofounder with Karl Marx of modern Communism. In The
Origin of the Family: Private Property and the State,
Engels argued: “Monogamy arose through the concentration
of wealth in one hand – a man’s hand – and
from the endeavor to bequeath this wealth to the children of
this man to the exclusion of all others.” The only
way to establish the children as his own was to have monogamy. The
rule of paternity presumption, he wrote, was necessary to resolve
the conflict between “irrepressible” acts of adultery
and the father’s goal of establishing the certainty of
paternal parentage.

In
providing his explanation, Engel had assumed that a father was
instinctually motivated to hand down his wealth to his children. Is
this a reasonable assumption to accept? The first step
in answering this question is to recognize that the family, like
other social organizations and behaviors, is an adaptation that
arose through natural selection. The idea that human behavior
and social structures are products of evolution is not new. Ever
since Darwin proposed his theory of evolution, scientists – including
Darwin himself – have wondered about the relationship between
genes, behavior, and natural selection. Making the connection
between natural selection and family organization means that
rather than looking at it as an arbitrary lifestyle, the family
can be viewed as intimately associated with biology, and massaged
by natural forces of evolution and genetics.

The theory of evolution by natural selection was proposed by
Charles Darwin to explain the diversity of life observed on earth. In The
Origin of the Species, first published in 1859, Darwin introduced
the subject by discussing the process of animal husbandry and
domestication. He devoted its first chapters to establishing
how variations in physical attributes, such as color and fur
texture, that occurred spontaneously in domesticated animals
had been selected by breeders to improve their utility for human
purposes. He described various examples where breeders
had observed the appearance of desirable favorable traits in
particular animals, and selected these animals for further breeding. Over
very few generations, human breeders had successfully modified
the appearance of many animal and plant species to a considerable
extent. Pigeon breeding was a popular hobby in Darwin’s
day. Darwin recounted how by selective breeding fanciers
had created wildly divergent birds, differing in color, feather
appearance, fantail, and beak. The same had been achieved
in dogs, sheep, horses, and plants. Whenever a trait that
struck man’s fancy or use appeared, a breeder could select
it, and by meticulous breeding, incorporate it into the breed. Darwin
reasoned that if humans could accomplish so much over a relatively
short period of time, then nature ought to be able to achieve
even more dramatic transformations over hundreds of thousands
of generations. Using this as starting point, Darwin laid
out his theory of natural selection, the theory that nature selects
for those traits that facilitate and enhance an organism’s
ability to survive and reproduce in its environment.

A fundamental tenet of Darwin’s theory is the existence
of variations in phenotype among individuals of the same species. Nature
acts by scrutinizing and choosing from among the natural differences
between individuals those which confer the most benefit in the
individual’s effort to survive and reproduce. In
turn, these traits are passed on to their progeny, and in time,
become firmly fixed in the species, leading to gradual changes
in the species’ physical characteristics – its phenotype. Reiterative
cycles of variation, selection, and reproduction, explain the
gradual evolution of one species into another. Speciation,
and the associated observed diversity in animal and plant life,
is a response to pressures in the environment – the conditions
and organisms that are encountered in day to day living. This
includes others of one’s own species, as well as predators,
parasites, food sources, and each and every organism encountered
during one’s life.

Darwin did not understand the genetics of hereditary, but he
recognized that, for evolution to be move forward, favorable
characteristics had to be passed on from parent to offspring. At
the time Darwin was formulating his theory of evolution, another
giant in the field of biology – Gregor Mendel – was
carrying out experiments that would establish the foundation
of modern genetics. In the classic experiments on peas
performed by Mendel from 1857 to 1863, he found that each physical
trait of the plant was controlled independently by its own unique
pair of factors that he called “elementen.” These
elementen are now known as genes. Each parent packages
half of its genes into its gamete – the egg and sperm. Upon
fertilization and conception, the embryo offspring inherits equal
parts of its mother’s and father’s genes. The
importance of Mendel’s work went completely unrecognized
during his lifetime. It wasn’t until the early twentieth
century when a new generation of scientists began to unravel
the mechanism of heredity that the buried genius of his work
was discovered.

The relationship between genes and behavior broke new ground
in the 1970’s, when biologists working with the simple
fruit fly, first identified genes that affected basic behaviors,
such as learning and courtship. With names like dunce and
rutabaga to signal their inability to learn, genetic strains
of flies were isolated that permitted scientists for the first
time to identify the genes underlying seeming complex behaviors. As
more sophisticated technologies were developed, this work was
extended to mammals. Using combinations of genetic technology
and careful tracing of family histories, a collection of genes
have now been identified which influence behavior in animals,
including humans. In most cases, especially in humans and
other mammals, it is known that a particular gene has an effect
on a behavior, but its precise mechanism has not been worked
out.

In the animal kingdom, there are many examples of communities
with complex social organizations that appear to be entirely
a product of genetic factors evolved during the process of natural
selection. Social insects are highly cooperative societies
in which members are organized into distinct castes, each caste
performing a defined role necessary to promote the community’s
success. One or more queens are the fertile individuals
bearing primary responsibility for procreation. Worker
and soldier castes are infertile, carrying out the business of
the group – harvesting food, taking care of the larvae,
and defending the group against invaders. A gene has been
identified in the social insect, fire ants, that appears to regulate
whether a colony will have single or multiple queens. When
individuals have one form (“allele”) of the gene,
the colony is ruled by a single queen, but when they have another
form of it, several cooperative queens are found reigning in
the nest. Krieger and Ross, Science, 295:328,
2002. Thus, social structure is a very simple animal society
is determined directly by a single gene carried by the community
members.

Natural selection works the same way on behavioral characteristics
that it operates on physical traits. To put it in evolutionary
terms, behaviors that lead individuals to succeed in the struggle
to survive and reproduce are inherited by their progeny, and
through many generations of reproductive success, disseminate
throughout the population.

But how does this help us understand family law? First,
we need to recognize that laws are utilized by a society to influence
and shape the individual’s behavior to achieve certain
goals and priorities set by the policy makers. Rules that
make parties responsible for their conduct act as a deterrent,
discouraging the kinds of behavior that society considers harmful. By
imposing a penalty on bad behaviors, the law’s goal is
to change human conduct. Tort law provides an obvious example
of a legal construct that regulates behavior. To encourage
behaviors that minimize accidents, liability is placed on the
party who is in the best position to avoid, or reduce, injury. This
encourages individuals to take necessary precautions to prevent
accidents from happening in the future. Contract law follows
the same principles. The goal of each party to a contract
is to maximize his wealth. For everyone to be better off,
we want to encourage parties to keep their contractual promises,
and breach only when it is economically efficient. As a
consequence, individuals who break their promises are held liable
for the economic damages that flow from their bad conduct. In
each case, the law’s purpose is to maximize resources that
society considers valuable. It achieves it by formulating
rules that encourage resource maximizing behaviors.

Behavior forms the bridge between the legal system and natural
selection. The legal system – the laws, statutes,
and judicial decisions that comprise it – is aimed squarely
at human behavior, and human behavior is a consequence of evolution.
Appreciating this connection is the small part of the story. The
bigger issue is how to define the character of the relationship
between the two. It is evident that the human legal system
is not directly determined by single genes in the same way that
a fire ant society is dependent upon which gene allele is possessed
by community members. But how do the two fit together? Behavior
in humans and in animals is a complicated business driven by
the interaction of many different genes that operate in the depths
of the brain. Behaviors, and the genes which underlie them,
are more likely act more as guiding principles that either restrain
or promote the likelihood of certain rule-making.

The starting place for an analysis of the relationship between
evolution and the law is to consider what kinds of behaviors
would be expected to be favorably selected by evolution, and
then to explore how the law treats these behaviors. Reproductive
behavior is an obvious place to begin the inquiry since reproduction
is so essential to the evolutionary process. Without reproductive
success, favorable traits would not be carried forward, and an
individual would lose the ability to contribute to the species’ evolving
look. Given this significance, it is logical that reproduction
is a target of the law, and that the family – as the basic
unit of reproduction in the American legal system – is
a central pawn in the regulatory scheme.

The conflict between the sexes

One of Darwin’s key observations was that individuals
are in struggle to survive – against individuals of the
same species, of different species, and against the physical
environment, itself. Conflict is therefore a basic element
of evolutionary theory. Included in it, is the reproductive
struggle between species members. We compete with each
other for reproductive partners. Characteristics that facilitate
reproductive competition and success – good looks, fertility,
and the ability to provide for a family – are passed on
to progeny, gradually accumulating over time, displacing less
beneficial traits in the population. The key point to ponder
is how these evolutionary principles are applied in the law. For
this reason, we need to spend some time on understanding their
basic workings.

Conflicts between the sexes begin with the differences in the
investments they make in their quest for progeny. Female
investment in a single reproductive event is, for the most part,
much higher than the male’s. The key jewel is the
female’s egg. In oviparous organisms that lay eggs – like
birds and reptiles – she is responsible for manufacturing,
and depositing into a fully formed egg, the entire energy source
necessary for the embryo to develop from a single cell into the
multi-cellular offspring that eventually hatches from it. Viviparous
organisms – including humans and other mammals – have
as difficult a task. They produce live offspring directly,
and the mother must continuously provide nutrients to her child
until it is ready to emerge into the world.

The father, in stark contrast, usually gives his embryonic child
only a small package of genetic material – a spark to initiate
embryogenesis – but no nutritive resources. Even
the cellular machine to make energy – the mitochondria – comes
from the mother. Instead of expending the considerable
energy that his partner does on providing for the embryogenesis
of the nascent child, the male strategy is to father as many
children as possible with the hope that at least a few make it
to adulthood. With this strategy, a male has a lot less
to lose when he makes a bad choice of a particular mother for
his child. If he has played his cards right, he has placed
his bets on a number of fertile women willing to provide food
for his developing baby. Failure of one or two would not
terminate his reproductive output for that season.

A female, whether she is oviparous or viviparous, must sock
away valuable resources and time in carrying out the reproductive
process to its successful completion. Her reproductive
output is limited by how many eggs she is capable of producing. She
doesn’t produce the swarm of gametes that a man does, instead
concentrating on a few good eggs. If she errs in choosing
a father for her child, she looses far more than the male because
it can mean starting all over again. Females who
acquire adaptations that guide them in “good” mate
choice – fathers whose genetic material enhance the babies
own survival and reproductive success – are ultimately
more successful, passing these mate preference adaptations on
to future generations.

The disparity between male and female investment is good reason
for battles between the sexes. To increase their reproductive
output, all males have to do is chase and impregnate as many
females as possible. The number of females they can find
limits their reproductive output. As a result, characteristics
that enhance their appeal to females become important vehicles
to success. This is the basis for what has become known
as “sexual selection.” A female’s taste
in males ends up being reproduced in her male offspring because
he is the kind of mate she chooses to father her children, and
as a consequence, his appealing qualities end up immortalized
genetically in any progeny they co-produce. The females’ selection
of male traits eventually shapes the appearance and behavior
of the male population.

How does a female choose a father for her child? Potentially,
she can discriminate between males based on their possession
of economic or genetic resources. In many species of birds,
males compete with each other to establish territories that are
rich with the resources to provide to their progeny. Success
in acquiring territory translates into reproductive success because
it increases the likelihood of being chosen to father a fertile
female’s brood.

While recognizing whether a male is economically well off may
be relatively easy, how does a female chose a male for his good
genes? In a study of European starlings, it was discovered
that male birds who sang the loudest and longest also had the
strongest immune systems. Duffy and Ball, Royal Soc.
Lond B, 2002. Females selecting the premium crooners
from the crowd were also picking the males with the greatest
resistance to disease and infection. Bird song was therefore
a proxy for the male’s good health, and presumably for
the good genes responsible for it. The same explanation
has been offered for the observation that females in several
bird species prefer males with elaborate ornaments. Krebs
and Davies, An Introduction to Behavioural Ecology,
Third Edition, Blackwell Science, 1993, Pages 188-197. Male
peacocks, birds of paradise, and pheasants, to name a few, have
evolved extravagant feather displays that are used to attract
reproductive partners. According to one theory, ornament
exhibition by males is a method by which they show off their
genetic resistance to disease and disability. Males who
are able to bear the physiological costs of elaborate body ornaments
are more likely to be healthy individuals possessing good genes.

The law favors reproductive success

The law recapitulates the conflicts between and among the sexes
that evolutionary theory predicts. After all, the law is
about regulating behavior. Just as tort law encourages
people to take proper precautions to avoid accidents, we might
expect that family law promotes reproductive success. In
disputes that involve families, and other relations between women,
men, and, their children, the aim – from the Darwinian
perspective – is to find an outcome that favors reproductive
efficiency. This leads to the question of whose reproductive
capability does the law protect. In the paternity presumption
rule raised in the Michael H. case, it’s the mother’s
interest which appeared to be favored. Michael lost his
bid for fatherhood. Gerald was stuck supporting a kid who
wasn’t his own. But Carole won out because she got
to choose who would contribute the genes to her child, and who
would be the best provider for it. Michael also got away
like bandit. He successfully procreated, but at little
cost to himself. Gerald may have ended up with the worst
deal since he was left responsible for Michael’s child,
but, of course, he did get Carole, and continued reproductive
opportunity with a woman who had proven herself fertile. Considering
that the law shaping this strange deal was made exclusively made
by men, it’s intriguing that it’s Carole who gets
the best end of the bargain. But more on this later.

In explaining the origin of the paternity presumption rule,
Engels stated that men sought to bequeath their wealth to their
biological children. From an evolutionary viewpoint, this
seems like a reasonable proposition. Consider the case
where there are two kinds of males – males who prefer to
share their money with their biological children, and males who
don’t care, and give it away indiscriminately. Assume
that this behavior is somehow genetically coded, making it an
inheritable trait. Kids who get the wealth are better off,
and more successful reproductively than those who don’t
get it. Under these conditions, the kids with dads who
keep the money in the family will end up with more children of
their own, than the kids whose fathers don‘t care. Not
only will the kids with generous dads do better, but they and
their own progeny will exhibit the same favorable trait, having
inherited it from their father. After many generations,
this behavior would predominate in the population, becoming the
behavioral rule.

The same logic that resulted in the selection of men who passed
wealth on to their own natural children would apply similarly
to women. But there’s even another factor that is
as interesting. Let’s say that females are more likely
to select a mate who has the quality of willing his wealth to
his children, rather than a man who gives it up arbitrarily. This
would make sense when money is advantage. The female’s
choice becomes an additional and potent selection factor, further
enhancing the reproductive potential of the man who shares his
wealth only with his family. Since she only chooses men
who practice nepotism toward their children, men who don’t
tend to be fruitless. This facilitates the spread of the “nepotic” genes,
while impeding those of the arbitrary man. The behavioral
trait becomes fixed in the population, as Engels had argued. Engels
blamed the man entirely for the emergence of monogamy, but this
analysis predicts that the woman has equal culpability.

According to this theory, men – by hard-wired inheritable
instinct – would tend to give resources away to their biological
children. If this behavioral rule is embedded in the man’s
psyche, what kind of legal code should we expect to be erected
around it? One approach is to enact laws that effectuate
choices that a person would have made had he the opportunity,
but who is deceased or otherwise incapacitated. In this
case, the solution is quite clear. Our evolutionarily-tuned
rule maker codifies his instinct by adopting a law that vests
a decedent’s wealth in his kids. As predicted, most
states codify the practice. When a father dies without
a will, his children are automatic potential beneficiaries. We
will return to this topic later on.

There is no single reflection of evolution in the law. One
class of rules are those that codify practices which are in the
best interest of a person’s reproductive goals. The
point of this kind of rule is to protect the individual’s
interest from intrusion by the state. An example of this
is illustrated in Skinner v. Oklahoma described in Chapter
2. In another reflection, the law executes choices for
a person who is dead, incompetent, or otherwise incapacitated. The
laws of estate succession are a good example. A third category
comprises rules which codify behaviors contrary to those which
have been evolutionarily selected. An example of this arises
in circumstances where there is a conflict between the male and
female reproductive interests, and the law favors one sex. As
discussed later, abortion laws fall into this group.

In
the selection of cases presented here, principles of evolutionary
biology are applied to legal conflicts that arise in the context
of human sexuality in disputes over procreation rights, paternity,
parenthood, ownership of sperm, and sexual orientation. Evolutionary
theory fits into evolutionary jurisprudence by providing a foundation
to frame questions about the impact of laws on reproductive behaviors,
and to ask whether a particular law is consistent with the reproductive
interests of the players involved. In reading the cases
which follow, consider whether the law has been crafted to support
an individual in his drive to reproduce and express his sexuality.